Method and apparatus for use in electrolytic shaping



June 14, 1966 A. WILLIAMS 3,256,165

METHOD AND APPARATUS FOR USE IN ELECTROLYTIC SHAPING Filed June 19. 1961 2 Sheets-Sheet 1 Fawn/L ar fi yizn VL illama June 14, 1966 T wlLLlAMS 3,256,165

METHOD AND APPARATUS FOR USE IN ELECTROLYTIC SHAPING Filed June 19. 1961 2 Sheets-Sheet 2 United States Patent 3,256,165 METHOD AND APPARATUS FOR USE IN ELECTROLYTIC SHAPING Lynn A. Williams, Winnetka, Ill., assignor to Anocut Engineering Company, a corporation of Illinois Filed June 19, 1961, Ser. No. 117,941 14 Claims. (Cl. 204-143) This invention relates to methods and apparatus for use in systems for electrolytic shaping of conductive materials. More particularly, the invention is directed to methods and to apparatus for removing metals and metal salts from the electrolyte used in electrolytic shaping systems. Such metals and metal salts build up in the electrolyte as a result of the anodic dissolution of the workpiece being shaped.

Electrolytic shaping techniques to which the present invention finds application utilize a shaping electrode that is preferably maintained in closely adjacentspaced relation to the workpiece to provide an electrolyte work gap. A highly conductive electrolyte, ordinarily in the form of an aqueous salt solution, is caused to flow through the gap under high pressure to accommodate a high density current flow through the gap with a minimum voltage drop between the shaping electrode and workpiece.

As the current is passed through the electrolyte between the electrode and the workpiece, anodic dissolution of the workpiece occurs and metal and metal salts may go into solution in the electrolyte. In the conventional procedure, the electrolyte is collected and recirculated through the gap separating the shaping electrode and the work piece. As the electrolytic shaping process progresses, the metal salt content of the electrolyte tends to increase. Ultimately the concentration of these metallic salts could reach a value such that several undesirable reactions can become important.

Associated with the build up of metal salt concentration in the electrolyte is an increase in the tendency for metals and metallic salts to plate on or to be deposited on the shaping electrode. An important detrimental result of such deposition is that the configuration of the shaping electrode is distorted. When this occurs, the electrode is no longer capable of producing the intended shaping of the workpiece. Moreover, as deposits build up on the shaping electrode, the gap between the shaping electrode and the workpiece becomes altered and irregular. Local overheating, pitting, corroding, and even arcing and sparking may occur. The electrode and the workpiece may be irreparably damaged and the electrolytic shaping process may lose its many important advantages.

' Among the objects of the invention are the following:

To provide novel methods and apparatus for removing metals and metal salts from the electrolyte employed in electrolytic shaping systems;

To provide a method and apparatus wherein the same current that eifectuates the anodic dissolution of the workpiece is passed through a plating system for removing the metals and metallic salts from the electrolyte used in the electrolytic shaping system;

To provide methods and apparatus for preventing the deposition or plating of metals and metallic salts on the shaping electrode by utilizing the current that produces anodic dissolution of the workpiece to also cause removal of these metals and metallic salts under controlled conditions in an isolated plating system;

To provide automatic voltage regulation for an electrolytic system wherein the anodic dissolution current is also passed through a plating system that is capable of introducing undesired voltage changes at the work gap;

To provide a method and apparatus for removing metals and metal salts from an electrolyte used in an electrolytic shaping system wherein the pH of the electrolyte in the plating bath is preferentially adjusted to facilitate eflicient removal of such metals and metal salts;

To provide a method and apparatus for removing metals and metal salts from an electrolyte used in anelectrolytic shaping system wherein the electrodes in the plating bath have a graduated spacing to adapt them to various dif- V ferent electrolytic systems and electrolytic conditions;

To provide a method and apparatus for removing metals and metal salts from an electrolyte used in an electrolytic shaping system wherein a plating bath removes soluble salts from the electrolyte and a mechanical separator re- 7 moves insoluble salts.

Other objects and advantages will become apparent during the course of the following description.

In the accompanying drawings forming a part of this specification and in which like numerals are employed to designate like parts throughout the same;

FIG. 1 is a schematic diagram illustrating a preferred form of apparatus used in this invention;

FIG. 2 is a partial schematic diagram of an alternative power supply system and includes a vertical sectional view illustrating a preferred form for the electrodes of the plating system of the invention;

FIG. 3 is a partial schematic diagram of still another power supply system and includes a vertical sectional view illustrating an alternative form for the electrodes of the plating system of the invention;

FIG. 4 is a side elevational view of an alternative platingd bath equipped with self-scraping rotatable electrodes; an

FIG. 5 is a horizontal view partially in section and may be considered as taken in the direction of the arrows substantially along the line 5--5 of FIG. 4.

Referring now to the drawings and particularly to FIG. 1, a shaping electrode 10 is shown schematically as connected electrically to 'an electrode holder 11 whichis in turn connected to an insulating block 12. The insulating block 12 is attached to a mounting plate 13 fastened to the extended end of a ram 14 protected by a collapsible boot 15. The ram projects from a drivehead 16 for powering the advance of the electrode 10. Spaced closely adjacent the working face'lllF of the shaping electrode 10 is a workpiece W shown schematically as connected to an electrically conductive support 17. An electrolyte gap 21 is defined between the workface 10F of the shaping electrode 10 and the workpiece WI Electrolyte 22 is shown being delivered to the electrolyte gap 21 through a channel 23 in the shaping electrode 10' by a pressure pump 24 connected in a line 25 leading from a storage tank 26.

The invention is applicable to systems such as the electrolytic cavity sinking arrangements shown in my application entitled Electrolytic Shaping, Serial No. 772,960, filed November 1-0, 1958 now Patent No. 3,058,895 wherein electrolyte is supplied through a hollow electrode. The types of electrolytes disclosed in my aforesaid application are contemplated for use in the present arrangement. It is essential, however, that the electrolyte used be capable of forming soluble salts of the metal of the work material. For working steel, a simple sodium chloride solution will remove the metal but the salts formed go over quickly to insoluble iron hydroxide. For purposes of this invention, the solution should contain enough of a complexing agent, such as sodium or potassium citrate or Rochelle salts to form soluble salts of iron. Tests have shown that the iron can be deposited from such a solution. There are, of course, many other solutions which will form soluble salts of the work metal. In successful tests the following so1ution has been used: To five gallons of water add:

Potassium chloride 10 pounds (3 parts). Potassium nitrate 3 /3 pounds (1 part). Rochelle salts 3 /3 pounds (1 part).

Potassium citrate 3 /3 pounds (1 part).

Patented June 14, 1966 Either the electrode or the workpiece or both may be movable. After the electrolyte flows through the work gap 21, it is collected in a pan 27 and returned to a plating or deposition tank 28 thorugh a conduit 29 connected at a drain area 30 of the collector pan or tank 27. The electrolyte 22 is returned to the storage tank 26 by means of a pump 31 connected in line in a pipe 32 connecting the plating tank 28 and the storage tank 26. Thus, the electrolyte is continuously cycled from the storage tank 26 through pressure pump 24 and tube 25, through the shaping electrode and through the work gap 21, whereupon it is collected in the pan 27, delivered to the plating tank 28, and finally returned to the storage tank 26 by means of conduit 32 and pump 31.

To provide for adjustment of the throughput capacity of the pressure pump 24, a bypass line 25L equipped with a manual return valve 25V is connected into the pressure side of the pump 24 and leads to the storage tank 26 to return a portion of the liquid electrolyte. A pressure gauge 25P is provided on the pressure side of the pump to indicate the proper setting for the manual return valve 25V.

The storage tank 26 may be provided with a mechanical agitator 33 and with a cooling coil 34. A thermostatic probe 35 projects into the electrolyte in the storage tank 26 and is connected to a control element 36 which is in turn connected to a thermostatic valve 37 for regulating the supply of cooling water through cooling coil 34.

In FIG. 1, a pipe 38 is shown connected to draw off electrolyte from the storage tank 26. At its other end,

the pipe 38 feeds into the electrolytic plating tank 28.

Thus, in the embodiment depicted, electrolyte 22 flows from the storage tank 26 through the tube or pipe 38 to the plating tank 28. This parallel electrolyte path between the storage tank 26 and the plating tank 28 may be omitted in other arrangements. However, in the particular arrangement shown, in addition to providing continuous circulation of electrolyte from the storage tank 26 to the work gap, and to the plating tank 28 and back to the sotrage tank 26, electrolyte is also continuously circulated between the storage tank 26 and the plating tank 28.

The plating tank is equipped with two sets 39 and 40 of inert electrodes with the electrodes of one set being arranged in alternating relation with the electrodes of the other set. One set 39, joined by a common bus bar 41, is electrically connected to the negative side 42 of a source 43 of D.C. power. The other set 40, which comprises the positive electrodes in the plating tank 28, is joined by a common bus bar 44 and is electrically connected over line 45 to the conductive support 11 for the shaping electrode 10. During operation of the device, the electrical circuit is completed across the gap 21 to the workpiece W. The workpiece W is connected to a line 46 leading to the positive terminal 47 of the source 43 of D.C. power.

As the electrolytic shaping of the workpiece progresses, the anodic dissolution of the workpiece causes an increase in the concentration of metals and metal salts in the electrolyte. Depending upon the composition of the workpiece itself, the metal salts may be the salts of iron, nickel, copper, or other metals of which the workpiece may be composed. As these salts build up in concentration in the electrolyte, there is an increased tendency for metals and metallic salts to deposit or plate upon the shaping electrode 10. In addition to changing or distorting the shape of the electrode itself, the result of metal plating or salt deposition on the shaping electrode is that the overall operation of the shaping system is impaired and the quality of the work is reduced. For some configurations in which the invention finds application, mechanical bridging between the shaping electrode 10 and the workpiece W may occur with the result that the workpiece will become pitted and corroded. avoided by preventing the build up of metallic salts in the electrolyte.

These undesirable conditions can be In the present invention this is accomplished by incorporating into the conventional electrolytic shaping system, the electrolytic plating bath that includes the tank 28 and the cooperating sets of electrodes 39 and 40. In this plating bath, the negative electrodes 39 act as plating electrodes. The voltage impressed across the positive electrodes 40 and the negative electrodes 39 causes the dissolved metal present in the electrolyte in the form of positively charged metal ions to be reduced at the negative electrodes 39 and to plate or deposit thereon.

It will be noted that in the illustrated arrangement the electrolyte emerging from the gap 21 is collected and first passed into the electro deposition cell or plating bath 28 before it enters the storage reservoir from which it is recirculated to the gap 21. In this arrangement, the electrodes in the plating bath are working on electrolyte solution having a relatively high concentration of metals and metal salts and this gives the most eflicient plating action in the deposition cell 28.

The plating cathodes 39 and the cooperating anodes 46 of the plating tank 28 are preferably of any large surface area relative to that of the electrode work interface be tween electrode 10 and the work W and provide a widely distributed current path therebetween in order to minimize voltage drop in the deposition tank and to facilitate the plating or deposition of metals and metallic salts on the cathode without a rapid build-up.

Any voltage fluctuations created between the cathodes 39 and anodes 40 in tank 28 tend to be reflected in corresponding voltage changes at the work gap 21.

In the embodiment shown herein for purposes of illustrative disclosure, the power supply is represented as having a three-phase line 48 feeding an input transformer 49 the' output from which is fed through a voltage adjusting element 50 which may be of the type utilizing saturable iron core reactance coils. In this arrangement, the source 43 of D.C. power may comprise a three-phase rectifier connected to the out-put from the voltage adjusting element 50.

It is important to maintain a relatively constant voltage across the gap between the shaping electrode 10 and the workpiece W. As mentioned previously, voltage fluctuan tions can result from the action in the plating tank 28 and,

accordingly, a voltage sensing and regulator element 51 is shown connected between the shaping electrode and the workpiece to sense the Voltage between them and to respond to any changes in this voltage for appropriately actuating the voltage adjusting element 50 to maintain the desired constant voltage across the gap 21.

Since the amount of current which passes through the work gap is identical with that which passes through the electrolytic deposition cell, the electrolytic deposition tends to occur at the same rate as the electrolytic removal in the work gap, and it is for this reason that the series connection is preferred. It is possible, however, to use a parallel connection, as shown in FIG. 2, or even to use a separate power supply 52 for the deposition cell, as is shown in FIG. 3.

While I have successfully plated out metal from the solution described above without need for chemical adjustr'nent, the plating reaction or the removal of metallic ions from solution in the plating tank 28 may, in some cases, be facilitated and favored by the adjustment of the pH of the electrolyte. For some metals, the addition of acid to the electrolytic solution facilitates the electroplating process. In the particular apparatus illustrated in FIG. 1 there is shown projecting into the solution in the plating tank 28 a pH sensitive and responsive probe 53.

The probe 53 is connected to a pH regulator 54 which is in turn connected to a control valve 55 operable upon demand to release acid 56 from a tank 57 into the plating bath of tank 28. The acid tank 57 is vented at 58 in the usual manner. The plating tank 28 may also be equipped with a mechanical agitator 59 for maintaining the solution therein homogeneous.

The electrolytic solution being pumped from the plating tank 28 through pipe 32 and entering the storage tank 26 may require a compensating pH adjustment before being supplied to the work gap 21. This pH adjustment, as shown in FIG. 1, is accomplished by means of a pH sensing probe 60 which projects into the electrolyte 22 of the storage tank 26. The probe 60 is connected to a pH regulator 61 which in turn controls the operation of a valve 62 to allow alkali 63 to flow from a tank 64 into the electrolyte 22 of the sump or supply tank '26. The alkali tank 64 is vented at 65 in the usual manner.

While the operation of the pH adjusting equipment shown in FIG. 1 has been described in connection with the addition of acid to the solution in the plating tank 28 and the addition of alkali to the electrolyte of the storage tank 26, it is possible that under some conditions, as for example when strong acids are used in the electrolyte, that it may be desirable to add alkali to the solution in the plating tank 28 in order to bring the pH of the solution to a preferred plating range. And, .in such a system, it may then be desirable to readjust the pH of the electrolyte in the storage tank by the addition of acid, before supplying the electrolyte to the work gap 21. Normally, however, it is preferred, where possible, to have a neutral solution in the work gap for ease in handling workpieces.

In the case of both the plating tank 28 and the tank 26, when the required pre-set pH has been achieved, the corresponding pH regulator will in each instance shut off the acid or the alkali control valve to terminate addition of reagent.

With some types of electrolytes in working in some types of metals the metal salts which results from electrolytic removal are not soluble, but, rather, they are insoluble. In some instances, this production of insoluble salts is believed to occur almost instantaneously in the work gap. In other cases, the insoluble salts may result from a secondary reaction. In a typical situation,'when the workpiece is made of steel and when the electrolyte is a simple solution of sodium chloride, the result will be to produce iron hydroxide, which is a solid but flocculent material. The solid material cannot be deposited in the electrolytic plating cell with any ease or satisfaction, and, accordingly, in such a work configuration it is desirable to use some form of mechanical separation. This may take the form of a surface filter, but it is preferred to use a centrifuge-for example, sold under the trade name Titan. This may be connected to the reservoir 26 or to the deposition tank :28, and it will remove the solid material. At the same time, it is common to find that this kind of electrolyte solution will contain some amount of soluble salts, either iron salts which have not converted to the iron-hydroxide form or, more often, the salts of alloying materials used in the steel. These metal salts which are soluble are then removed by the plating cell.

While, as pointed out above, a centrifuge or other device for the removal of solids from the electrolyte may be connected to the plating tank 28 or to the storage tank 26, or elsewhere in the equipment, as shown in FIGURE 1, in the preferred arrangement of the solids removal mechanism a centrifuge 66 is connected to the plating tank28 by means of a pipe 67. An in-line pump 68,

capable of handling solids, is connected in the line 67 between the centrifuge 66 and the lower portion of the plating tank 28 and supplies the feed to an inlet 69 of the centrifuge. The solid-free effluent is discharged through an orifice 70 of the centrifuge with the orifice 70 communicating with the plating tank- 28 through a pipe .71. The separated solids are periodically ejected through an opening 72 near the lower portion of the bowl 73 of the centrifuge and may be reclaimed or may be discarded, as desired. The centrifuge 66 is driven by a separate motor '74 coupled to the drive mechanism of the unit.

As the electroplating process continues in the storage tank 28, more and more material will deposit on the cathodes 39. From time to time it may become necessary to remove this deposit. This may be done by withdrawing theelectrodes 39 from the tank and scraping the deposit from the surface. In some instances the deposit recovered may have a value and will be saved; in other the deposit on them may be sent directly to a reclaiming and refining process.

InFIG. 1 theelectrodes 39 and 40 are shown schematically and are represented as being essentially planar. Such a configuration has actually been employed in the practice of this invention. For widespread commercial application, however an electrode configuration such' as is shown in FIG. 2 or in FIG. 3 is preferred.

In FIG. 2, the relatively thick graphite anodes 40 are shown planar while the thin sheet copper cathodes 76 have a corrugated form. Alternatively in FIG. 3 the relatively thick graphite anodes 77 are of scalloped or corrugated surface configuration and the sheet copper cathodes 39 are planar. The latter arrangement is preferred.

Depending upon the nature of the electrolyte and the concentration of metal salts as well as the kinds of metal salts, greater or less deposition will occur at varying degrees of separation between the anode and cathode plates. Since the purpose is to deposit all of the metals which may be present under whatever the existing conditions may be, the corrugations are provided so as to bring about spacing which ranges from being very close to being somewhat remote, so that whatever the nature of the electrolyte or the metals being worked or the operating conditions as to temperature and the like there will be'some gap dis. tance at which deposition will occur at high speed. It should be understood that no importance is attached to the quality of the plating, and in face the deposits obtained tend 'to be'brittle, frequently granular or flaky and of very poor quality as viewed in the ordinary electroplaters sense. However, it is possible because of the disregard for the quality of the plating to use higher current densitiesthan would otherwisebe chosen. The graduated spacing between the opposing electrodes in the arrangements shown in FIG. 2 and FIG. v3 increases the versatility and range of application of this invention and avoids the necessity of custom designing the equipment for each application.

To avoid the need for periodically removing the plating electrodes from the plating bath 35 for the purpose of scraping the deposit from the surface of these electrodes, an arrangement such as is shown in FIGS. 4 and 5 is contemplated wherein a set of scrapers 78 are mounted along a side edge of the plating tank in an arrangement that is capable of automatically removing the plating deposit as it is formed on the plating cathodes. As the deposit is scraped from the plating electrodes it falls into a tray or trough 79. The deposit so obtained may be reclaimed or may be discarded. In the particular form of apparatus shown in FIG. 4, a set of corrugated anode plates 77 are fixedly suspended in spaced apart parallel relation from a support and contact bar 80 that is fixed along a side edge of the tank 28. These plates may be rectangular and are substantially fully immersed in the electrolyte in the tank 28. A set of cathode discs 39 are interleaved with the anode plates 77 and secured in spaced apart parallel relation along a rotatable shaft 81 that is bridged across'the tank 28 at a location spaced slightly above the upper edges of the anode plates 77. The shaft 81isjournalled in side-mounted support bearings 83 and 84 and is driven by an external motor 85 to continuously rotate the discs 39. The rotating shaft is connected to the motor 85 by a belt 86 of insulating material. Electrical connection to the cathode discs is made through the shaft which is equipped with an external slip ring 87 and brushes 88. Insulating spacers 89 of a lubric plastic'material such as Teflon are interposed between adjacent discs and encircle the shaft. The scrapers 78 are positioned in the spaces between adjacent electrodes and in position to scrape against the rotating cathode discs 39. For this purpose the scrapers, which are preferably outside the tank, are shown anchored in a support structure 90 provided along one edge of the tank. The scrapers 78, which are preferably of non-conducting material, are continuously active to remove the deposits as they accumulate on the plating cathode discs 76.

Attention should be given to the materials used in the tanks and piping in the electrolytic shaping system of the invention. These materials should be selected with the recognition of the demands of the circulating electrolyte and with regard for the chemical reactions which are taking place in various portions of the system equipment. In general, the tanks are preferably made of glass reinforced plastic such as the epoxy resins. Hard rubber or rubbertype compositions are also suitable. While specially compounded chemically resistant metallic alloys may be used, these have certain disadvantages some of which are associated with the special precautions which would be necessary in order to insure adequate electrical isolation from the electrode systems involved. Electrical isolation requirements are most prevalent in the case of the tank 28 for the plating bath and it is therefore of principal importance that the plating tank be of an insulating plastic material or be lined with an insulating plastic material. The pumps and valves used may be selected from industrial equipment which has been found suitable in the handling of salt solutions and acidic solutions of the type involved in the electrolysis and the electroplating reactions occurring in the system of the invention.

While a disclosure of the preferred method and apparatus for the removal and control of salt deposition in electrolytic shaping operations has been provided, it will be apparent that numerous modifications and variations thereof may be made without departing from underlying principles of the invention. It is therefore desired by the following claims to include within the scope of the invention all such variations and modifications by which substantially the results of this invention may be obtained through the use of substantially the same orequivalent means.

In the appended claims, the term metalloid is used somewhat specially in referring to those electrically conductive materials which act like metals when connected as an anode in an electrolytic cell. The term includes metals and such similarly acting materials as tungsten carbide for instance, and distinguishes from such conductive non-metalloids as carbon.

I claim:

1. In electrolytic machining apparatus for removing material from a metalloid workpiece by means of an electrode having a conductive working face spaced closely adjacent said workpiece to define a .gap therebetween, means for supplying electrolyte through said gap to establish a high density current conducting path thereacross, means for collecting electrolyte emerging from said gap, and a circuit having rectifier means connectible to an A.C. supply for providing a low voltage source of direct current power connected in a sense to make the workpiece anodic and the electrode cathodic, said collecting means including means providing a plating bath having anode and cathode elements immersed in such collected electrolyte, with the collected electrolyte establishing a conducting path between said elements, and said circuit including electrical connections to said anode and cathode elements to establish said current paths in series circuit relation to plate simultaneously on to said cathode element metallic constituents tending to build up in said electrolyte as a result of electrolytic action upon said workpiece.

2. The arrangement claimed in claim 1 wherein certain areas of the anode and cathode elements of said plating bath are arranged to provide'varying spacing relationships between said elements.

3. The arrangement claimed in claim 1 wherein a set of anode elements are arranged in interleaved relation with a set of cathode elements, scrapers are positioned between anode and cathode elements in said bath for mechanical contact with deposits forming on said cathode elements, and means are provided for rotating said set of cathode elements to cause said scrapers to remove material depositing on said cathode elements.

4. In electrolytic machining apparatus for removing material from a metalloid workpiece by means of an electrode having a conductive working face spaced closely adjacent said workpiece to define a gap therebetween, means for collecting electrolyte emerging from said gap, means for supplying electrolyte from said collecting means through said gap to establish a high density current conducting path thereacross, and a circuit having a low voltage source of direct current power connected in a sense to make the workpiece anodic and the electrode cathodic, said collecting means including a separate plating bath, means for circulating said electrolyte through said bath, said bath having anode and cathode elements immersed in electrolyte contained therein, means for connecting direct current power to' said anode and cathode elements to plate simultaneously on to said cathode element metallic constituents tending to build up in said electrolyte as a result of electrolytic action upon said workpiece, means for preferentially adjusting the pH of electrolyte while in said plating bath to increase the efficiency of plating in said bath, and means for preferentially readjusting the pH of electrolyte before it is supplied from said collecting means to said gap to facilitate electrolytic machining at said gap.

5. In electrolytic shaping apparatus for removing mate-- rial from a metalloid workpiece by means of an electrode having a conductive working face spaced closely adjacent said workpiece to define a gap therebetween, means for supplying electrolyte through said gap to establish a high density current conducting path thereacross, means for collecting electrolyte emerging from said gap and including separate anode and cathode elements of large surface area immersed in such collected electrolyte, with the collected electrolyte establishing a widely distributed low density current conducting path between said elements, rectifier means connectable to an A.C. supply for providing a low voltage source of direct current, electrical connections connecting said current source, said workpiece, said electrode and said anode and cathode elements in a common circuit in a sense to make the workpiece anodic, the electrode cathodic and to establish said current paths in series circuit relation.

6. In electrolytic shaping apparatus for removing material from a metalloid workpiece by means of a shaping electrode having a conductive Working face spaced closely adjacent said workpiece to define a gap therebetween, means for supplying electrolyte through said gap to establish a high density current conducting path thereacross, means for collecting electrolyte emerging from said gap and including separate anode and cathode elements immersed in such collected electrolyte, with the collected electrolyte establishing a low density current conducting path between said elements, rectifier means connectible to an A.C. supply for providing a low voltage source of direct current, means for adjusting the output voltage of said source, electrical connections connecting said current source, said workpiece, said electrode, and said anode and cathode elements in a common circuit in a sense to make the workpiece anodic, the electrode cathodic and to establish said current paths in series circuit relation, and control means responsive to voltage changes across said gap and connected for controlling said voltage adjusting means to regulate the voltage at said source and maintain the voltage across said gap substantially constant.

7. In electrolytic shaping apparatus for removing material-from'a metalloid workpiece by means of an electrode having a conductive working face adjacent said work piece to define a gap therebetween, a plating bath receiving electrolyte emerging from saidgap and having anode and cathode elements immersed in electrolyte contained therein, with-the electrolyte in said bath establishing a low density current conducting path between said anode and cathode elements, an electrolyte storage reservoir, means for circulating electrolyte from said bath to said reservoir, andmeans for supplying electrolyte from said reservoir through said gap to establish a high density current conducting path thereacross, rectifier means connectible to an AC. supply for providing a source of direct current,

. and electrical connections connectingsaid current source to said workpiece, said electrode and said anode and-cathode elements in a common circuit in a sense to make the workpiece anodic, the electrode cathodic, and to establish said current paths in series circuit relation, means for preferentially adjusting the pH of bath electrolyte to optimize plating in said bath, and means for preferentially readjusting the pH of reservoir electrolyte before supply to said gap to facilitate material removal from said workpiece.

8. In electrolytic machining apparatus for removing material from a metalloid workpiece by means of an electrode having a conductive working face spaced closely adjacent said workpiece to define a gap therebetween, means for supplying electrolyte through said gap to estab lish a high density current conducting path thereacross,

means for collecting electrolyte emerging from said gap, and a circuit having a low voltage source of direct currentpower connected in a sense to make the workpiece anodic and the electrode cathodic, said collecting means including means providing a plating bath having anode and cathode elements of large surface area immersed in such collected electrolyte, with the collected electrolyte establishing a low density current conducting path between said elements, and said circuit including electrical connections to said anode and cathode elements to establish said current paths in series circuit relation to plate simultaneously on to said cathode element metallic constituents tending to build up in said electrolyte as a result of electrolytic action upon said workpiece, means for preferentially adjusting the pH of electrolyte while in said plating bath to increase the efliciency of plating in said bath, means for preferentially readjusting the pH of electrolyte before supply from said collecting means to said gap to facilitate material removal from said workpiece, means for adjusting the out-. put voltage of said" source, and control means responsive to voltage changes across said gap and connected for controlling said voltage adjusting means for regulating the source voltage and thereby maintain the voltage across said gap substantially constant.

9. In electrolytic machining apparatus for removing material from a metalloid workpiece by means of an electrode having a conductive working face spaced closely adjacent said workpiece to define a gap therebetween, an electrolyte storage reservoir, a plating bath .having anode and cathode elements of large surface area for immersion in electrolyte contained'therein, means for recirculating electrolyte from said storage reservoir, through said gap, to said bath and back to said reservoir to establish a high density current conducting path across said gap and a low density current conducting path through said bath, a low voltage source of direct current, electrical .connections connecting said current source, said workpiece, said electrode and said anode and cathode elements in a sense to make the workpiece anodic, the electrode cathodic and to establish said conducting paths simultaneously, means for preferentially adjusting the pH of bath electrolyte to optimize the efiiciency of plating in said bath, and means for preferentially adjusting the pH of reservoir electrolyte before supply to said gap to facilitate electrolytic machining at said gap.

- 1 01 In electrolytic machining apparatus for removing. material from a metalloidworkpiece by means of an electrode having a conductive working face spaced closelyadjacent said workpiece to define a gap therebetween,

an electrolyte storage reservoir, a plating bath having anode and'cathode elements oflargesurface area for immersion in electrolyte contained therein, means for re-.

circulating electrolyte from said'storage reservoir, through said gap, to said bath and back to said'reservoi'r to establish a high density current conducting path across said gap and a low density current conducting path through said bath, rectifier means connectible to an A.C. supply for providing a low voltage source of directcurrent', electrical connections connecting said current source, said Workpiece, said electrode and said'anode and cathode elements in a common circuit in. a sense to make the workpiece anodic, the electrode cathodic and to establish said conducting paths in series circuit relation, means for preferentially adjusting the pH of bath electrolyte to optimize the efliciency of plating in said bath, and means for preferentially adjusting the pH of reservoir electrolyte before supply to said gap to facilitate electrolytic machining at said gap.

11. In an electrolytic shaping process for removing material from a metalloid workpiece by means of a shaping electrode having a conductive working face spaced closely adjacent said workpiece to define an electrolyte gap for 'passing current therebetween, the method comprising conof current through an electrolyte from an electrode spaced a short distance away from the workpiece, the improvement which consists of concurrently depositing metal salts of the work material from the electrolyte as it is recirculated through an electrodeposition cell and through the work gap between the electrode and the workpiece, preferentially adjusting the pH of cell electrolyte to optimize the efiiciency of deposit of metal salts therein, and preferentially readjusting the pH of recirculated electrolyte before supply to said electrode and workpiece to facilitate material removal from said workpiece 13. In an electrolytic shaping process for removing material from a metalloid workpiece by means of a shaping electrode having a conductive working face spaced closely adjacent said workpiece to define an electrolyte gap for passing current therebetween, the method comprising continuously supplying, collecting, and recirculating electrolyte through said gap to establish a high density current conducting path thereacross, circulating electrolyte collected after emerging from said gap through a plating bath, serially passing the same current through said bath in low density form as is passed across said gap in high density form to plate out in said bath metallic constituents tending to build up in said electrolyte as a result of electrolytic action upon said workpiece, and adjusting the over-all applied DC voltage to maintain a constant voltage across said gap.

14. In an electrolytic shaping process for removing material from a metalloid workpiece by means of a shaping electrode having a conductive working face spaced closely adjacent said workpiece to define an electrolyte gap for passing current therebetween, the method comprising continuously supplying, collecting and recirculating electrolyte through said gap to establish a high density current conducting path thereacross, circulating the electrolyte that is collected after emerging from said gap through a plating bath, and serially passing the same current 2,748,071 through said plating bath as is passed across said gap to 2,772,232 plate out in said bath metallic constituents tending to 2,895,814 build up in said electrolyte as a result of electrolytic action 2,964,453 upon said workpiece, adjusting the pH of said electrolyte 5 3,002,907 while in said plating bath to optimize the efficiency of 3,003,942 plating out said metallic constituents, and readjusting the 3,004,910 pH of said electrolyte before supply to said gap to facili- 3,060,114 tate removal of material from said workpiece. 3,095,364 References .Cited by the Examiner 10 UNITED STATES PATENTS 1,937,179 11/1933 Weisberg 204--130 2,073,621 3/1937 Blaney 204-130 15 2,526,423 10/1950 Rudorff 204-143 Roehl et a1 204-238 Eisler 204--208 Comstock et al 204-218 Clark 204-143 Garn 204130 Williams 204-143 Cedrone 204130 Keeleric 204-143 Sanders 204-143 Faust et al. 204-143 OTHER REFERENCES A.P.C. application of Johannes Rzymkowski, Serial No. 338,261, filed June 1, 1943.

JOHN H. MACK, Primary Examiner.

P. SULLIVAN, R. GOOCH, R. HARDER, R. K. MIHA- LEK, Assistant Examiners. 

11. IN AN ELECTROLYTIC SHAPING PROCESS FOR REMOVING MATERIAL FROM A METALLOID WORKPIECE BY MEANS OF A SHAPING ELECTRODE HAVING A CONDUCTIVE WORKING FACE SPACED CLOSELY ADJACENT SAID WORKPIECE TO DEFINE AN ELECTROLYTE GAP FOR PASSING CURRENT THEREBETWEEN, THE METHOD COMPRISING CONTINUOUSLY SUPPLYING, COLLECTING AND RECIRCULATING ELECTRROLYTE THROUGH SAID GAP TO ESTABLISH A HIGH DENSITY CURRENT CONDUCTING PATH THEREACROSS, CIRCULATING THE ELECTROLYTE THAT IS COLLECTED AFTER EMERGING FROM SAID GAP THROUGH A PLATING BATH, AND SERIALLY PASSING THE SAME CURRENT THROUGH SAID PLATING BATH AS IS PASSED ACROSS SAID GAP TO PLATE OUT IN SAID BATH METALLIC CONSTITUENTS TENDING TO BUILD UP IN SAID ELECTROLYTE AS A RESULT OF ELECTROLYTIC ACTION UPON SAID WORKPIECE.
 12. IN THE PROCESS OF METAL WORKING BY ELECTROLYSIS IN WHICH MATERIAL IS REMOVED FROM A WORKPIECE BY PASSAGE OF CURRENT THROUGH AN ELECTROLYTE FROM AN ELECTRODE SPACED A SHORT DISTANCE AWAY FROM THE WORKPIECE, THE IMPROVE- 